1. Field of the Invention
The present invention relates to a camera for image pickup on a film and also for electronic image-sensing, and in particular, a camera for image pickup on a film and also for electronic image-sensing, functioning both as an apparatus for taking a picture on a film that takes an image of a subject on a silver halide film and an electronic image-sensing apparatus that has an image sensing device transforming the image of the subject into an electric signal.
2. Related Background Art
Conventionally, an apparatus for taking a picture on a film (hereinafter called a film camera) that uses a silver halide film is common as an apparatus for recording a subject as a still picture. In addition, as electronic technology has developed, a large number of apparatuses for electronic image-sensing such as digital cameras (hereinafter called digital cameras simply) have been commercialized. Here, the digital cameras each transform an electric signal, photoelectrically transformed from a sensed image of a subject (hereinafter called a subject image) by an image sensing device such as CCD, into a picture signal that is a digital signal. Further, the digital cameras each convert this signal into an image, display this as an image on a display unit such as an electronic view finder comprising an LCD, and record this on a recording medium like a memory device, etc.
These two apparatuses have merits and demerits respectively. Regarding high definition of a recorded image, the film camera is superior to the digital camera. However, the digital camera is superior in the fact that it can be confirmed at the time of image pickup what images were sensed or what their picture quality is. Thus, generally, the film camera can not determine at the time of image pickup whether the image taken on a film is taken in accordance with its photographer's intention.
Then, there are many proposals of cameras mutually supplementing respective demerits, that is, single-lens reflex types of cameras for image pickup on films and for electronic image-sensing. Thus, the cameras each expose a subject image on a silver halide film, and at the same time, guide a part of an image pickup light beam to an image sensing device using a half mirror or the like when this silver halide film is exposed by the light beam. Further, the cameras each fetch a picture signal of the subject, photoelectrically transformed by this image sensing device, as image data, record the image data in a memory medium like memory etc., and display the picture signal of the subject as an image on an electronic view finder or a display screen of a display unit after completion of exposure operation.
For example, Japanese Unexamined Patent Publication. No. 1-114169 discloses the technology of adding to a normal single-lens reflex type of film camera an image confirmation function for confirming a taken picture. Here, the function is added by changing the direction of a light beam of a subject (hereinafter called a subject light beam) with using a mirror interlocking with a shutter, forming the subject image on an image sensing device with an optical system, and sending to a display unit a picture signal generated by the image sensing device.
However, according to the means disclosed in the above-mentioned Japanese Unexamined Patent Publication No. 1-114169, it is possible to confirm the composition at the time of image pickup beforehand. Still, operation of the mirror is extremely complicated, and hence, it is very difficult to actually design it.
In addition, since an embodiment of the above-mentioned Japanese Unexamined Patent Publication No. 1-114169 adopts a transparent type of movable mirror, the light passing through an image pickup lens directly irradiates a shutter shade of a focal-plane shutter. Owing to this, light leakage from the shutter shade may occur, and exposure to a film may occur due to this. In addition, if the light passing through the image pickup lens is intense, shutter strips and the like may burn out. Further, since the above-mentioned Japanese Unexamined Patent Publication No. 1-114169 does not describe components for achieving auto-focusing such as a sensor for the auto-focusing, this invention can not apply to auto-focusing cameras as it is.
Incidentally, regarding a camera for image pickup on a film and for electronic image-sensing that is disclosed in the above-mentioned Japanese Unexamined Patent Publication No. 1-114169 and the like, it is necessary to execute exposure operation to a silver halide film and image-sensing operation to an image sensing device approximately at the same time. Thus, it is necessary to execute steps of the exposure operation to a film and steps of the image-sensing operation to an image sensing device in parallel. The steps of the exposure operation to a film are mirror-up, diaphragm aperture setting, shutter driving, diaphragm aperture opening, mirror-down, shutter charging, and winding of a frame of the film. On the other hand, the steps of the image-sensing operation to an image sensing device are image-sensing with CCD, fetching of analog data, A/D conversion, recording in a memory device, and displaying on a display unit.
However, if the two different operations described above are simply executed in parallel, various malfunctions may occur that are caused by fluctuation of the power supply voltage, motor noises, vibration of movable members, and the like. In particular, if the mirror-up operation or mirror-down operation is performed during integrating operation of the image sensing device, the vibration may cause moving of the taken image, and the motor noise superimposed upon the electronically recorded picture signal may have a bad influence upon the picture signal.
Further, when a memorial picture including a person is taken with a film camera, the person who becomes a subject can not know the exposure timing of the film camera, and hence, the person may accidentally close his (or her) eyes at the time of exposure operation. Consequently, it is frequent that the image is regarded as a failed one. In this case, if the above-mentioned picture confirmation function is added to the camera, the photographer can confirm this failure with using this function, and hence, the photographer can relieve the failure by taking another picture.
However, in this case, if the time lag occurs between the image obtained by the electronic image sensing apparatus and the latent image on the film, the above-mentioned effect can not be obtained, and hence, relief of the failed picture can not be achieved.